Two structurally different oomycete MAMPs induce distinctive plant immune responses

Some molecular patterns unique to a certain group of microbes (MAMPs, microbe-associated molecular patterns) are sensed by plant cells as non-self molecules via pattern recognition receptors. This study aimed to identify unique MAMP elicitors from the oomycete pathogen Phytophthora infestans the causal agent of potato late blight. Using reactive oxygen species (ROS) production and phytoalexin production in potato as markers for the purification of oomycete elicitors we identified two structurally different groups of elicitors namely ceramides and diacylglycerols. P. infestans ceramide (Pi-Cer) elicitors induced ROS production while diacylglycerol (Pi-DAG) elicitors containing eicosapentaenoic acid (EPA) as a substructure induced the formation of phytoalexins in potato. When Arabidopsis was treated with Pi-Cer and EPA partially overlapping but different sets of genes were induced. Furthermore simultaneous treatment with Pi-Cer and EPA did not have a cumulative effect on induced genes but rather the expression of some genes induced by EPA was attenuated by the co-treatment with Pi-Cer.